Abstract
Targeted light delivery into biological tissue is needed in applications such as optogenetic stimulation of the brain and in vivo functional or structural imaging of tissue. These applications require very compact, soft, and flexible implants that minimize damage to the tissue. Here, we demonstrate a novel implantable photonic platform based on a high-density, flexible array of ultracompact (30 μm × 5 μm), low-loss (3.2 dB/cm at λ = 680 nm, 4.1 dB/cm at λ = 633 nm, 4.9 dB/cm at λ = 532 nm, 6.1 dB/cm at λ = 450 nm) optical waveguides composed of biocompatible polymers Parylene C and polydimethylsiloxane (PDMS). This photonic platform features unique embedded input/output micromirrors that redirect light from the waveguides perpendicularly to the surface of the array for localized, patterned illumination in tissue. This architecture enables the design of a fully flexible, compact integrated photonic system for applications such as in vivo chronic optogenetic stimulation of brain activity.
Highlights
From biological science to clinical practice, optical methods for imaging[1,2,3] and manipulation[4,5,6,7,8,9] of tissue are the gold standard for noninvasive interaction
Parylene photonics can be broadly used in any biomedical application, here, we focus on device design in the context of neural stimulation using optogenetics
The Parylene photonics platform operates over a wide range of wavelengths, especially in the visible range that is relevant for optogenetic stimulation of neural activity
Summary
From biological science to clinical practice, optical methods for imaging[1,2,3] and manipulation[4,5,6,7,8,9] of tissue are the gold standard for noninvasive interaction. The scattering and absorption of light in tissue pose fundamental limitations to the achievable resolution and depth of penetration. Multiphoton techniques, which utilize simultaneous absorption of longer wavelength photons to activate visible-range optical agents, achieve deeper penetration into tissue due to reduced attenuation of near-infrared and infrared light. In the context of brain imaging and manipulation, accessing deeper regions is required to study the neural mechanisms of disorders such as Parkinson’s disease that involve malfunction of circuits in deep structures, namely, the basal ganglia nuclei. Implantable devices, which enable targeted light delivery deep into tissue, are needed to advance scientific understanding of biological mechanisms and to aid clinical intervention
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